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biological indicators such as the appearance of commensal species. The appearance of large habitation sites with thick cultural deposits and rich material remains, including architectural features, ornamentation, art, and conspicuous human cemeteries, also sets the Natufian apart from all preceding Paleolithic cultures (Bar-Yosef and Belfer-Cohen 1991; Henry 1989; Tchemov 1991). The large "base camps" of the western Mediterranean hills (cf. Bar-Yosef 1970) form the core of arguments for the appearance ofsedentism and population pressure in the Natufian period; thus they are the focus of study here. Although many archaeologists would agree that sedentism, intensified resource use, and human population growth were present in the Levant by the Early Natufian phase, no adequate measure of their magnitude or implications for the emergence of agriculture has been developed.
By definition, sedentism refers to the settling down of human populations into permanent or semi-permanent residential camps (Hitchcock 1987; Kelly 1995). This study prefers the term "site occupation intensity" to the term sedentism, because the former is better suited for distinguishing relative differences in site use, both between cultural periods and within the Natufian period itself. The intensity of site occupation is undoubtedly one of the most enthusiastically studied archaeological questions of the Natufian period (Bar-Yosef and Belfer-Cohen 1989, 1991; Belfer-Cohen and Bar-Yosef 2000; Davis 1983; Edwards 1989; Kaufman 1989; Lieberman 1991, 1993; Rosenberg 1998; Tchemov 1984, 1991). Researchers want to determine if Natufian populations had settled down or not, and if so, whether they lived in permanent villages for the entire year
investment in a habitation site, such as the presence of architecture, and the presence of commensal animals. Though suggestive, the results of these studies remain inconclusive, because the indicators used are unable to prove year-round occupation or distinguish among degrees of site occupation intensity. Clarifying the degree of site occupation intensity during the Natufian period in demographic terms will also shed light on the role of other factors such as human subsistence strategies, population growth, social organization, and cultural complexity in the Natufian period.
If we are to reconstruct the human demographic and economic environment during the Natufian period and evaluate its role in the transition to agriculture, then new methods must be implemented to quantitatively test these questions. Although this study builds upon previously published concepts ( Stiner, Munro and Surovell 1999, 2000), it differs in application because it focuses principally on site occupation intensity, spatial variation in the indications of predator pressure, and small-scale diachronic variation within a single cultural period.
This research applies ecological models to the Natufian archaeological record to test if population pressure, sedentism, and intensified resource use were already in existence, and hence possible catalysts for economic change prior to the transition to agriculture. The theoretical basis for the research is rooted in population ecology and draws heavily on the principles of foraging theory (optimization models) and predator
directly translate into changes in the intensity with which humans use local resources, including wild animals. Higher densities of people mean that greater quantities of resources must be harvested each year. Sustained pressure on resources may eventually lead to the depression and restructuring of local plant and animal communities (e.g., Broughton 1994; Speth and Scott 1989). Humans must respond to self-induced disturbances in resource distribution and abundance by altering their foraging regimes to include less desirable resources.
This research predicts the potential effects of human hunting on prey populations specifically, the effect of varying degrees of hunting pressure upon prey availability and age structures — and then seeks these signatures in the archaeological record. The relationship between predators and their prey has been studied in ecology for many decades (e.g., Berryman 1992; Blasco et al. 1986/87; Dye et al. 1994; Elton and Nicholson 1942; Lambert 1982; Pianka 1978; Solomon 1949), but this rich literature has rarely been applied to the reconstruction of past human/animal relationships (but see Botkin 1980; Broughton 1994; Christenson 1980; Earle 1980; Stiner et al. 1999, 2000;
Winterhalder et al. 1988). Because the prey species hunted by humans in the Natufian period still exist today, modem ecological data provide an independent framework for interpreting patterns in the archaeological record.
Optimality Theory and Predator-Prey Simulations Optimality models make predictions about the behavior of consumers according to the assumption that natural selection will lead individuals to make decisions that
MacArthur and Pianka 1966; Perry and Pianka 1997; Pyke et al. 1977; Schoener 1971;
Stephens and Krebs 1986). In ecology, optimality models are most often incorporated within a body of research known as foraging theory, and are designed to predict the decisions made by living species during resource procurement. Although the formal conditions of foraging theory are not employed here, the basic principles are used to generate qualitative predictions about past human foraging behavior.
The energy equation that predicts which animals human hunters will prefer is a simple cost/benefit function measured in calories. Benefits are derived from the energetic returns of the animal captured, and costs include the relative energy expended by the hunters on search, pursuit, and handling (Chamov 1976; Pianka 1978; Stephens and Krebs 1986). Search costs refer to the energy expended while locating prey; pursuit costs concern energy spent on the capture of the animal once it is located; and handling denotes the energy required to prepare the animal for consumption (i.e., transport, processing, cooking). To maximize reproductive fitness, human hunters are expected to prefer animals that provide the highest net energy returns (high-ranked species) after the costs of search and capture are taken into account. Only when demand exceeds the availability of high-ranked resources are hunters expected to turn to species that provide lower net returns (low-ranked species).
Ranking prey Understanding the conditions under which prehistoric animal assemblages were generated requires that common prey species be raiiked relative to one another. In
Griffiths 1975; Sirruns 1987; Szuter and Bayham 1989). The larger the animal, the higher its ranking since all are made of the same range of tissues. In most cases body size is an effective measure of rank because the caloric value of large animals tends to be high enough to substantially outweigh the cost of capture. However, these rankings are based entirely on the benefit part of the equation, and the role of cost is ignored. In cases where capture costs are quite low, animal resources should be collected when encountered, regardless of body size. In effect, these resources provide pure gains, especially if the search is embedded in other foraging agendas. This is underscored in recent work by Stiner et al. (1999, 2000), who argue that slow-moving animals such as tortoises and shellfish may be high-ranked species despite their small body sizes. As such, they are expected to regularly enter the diet when encountered. Both the escape strategy and body size of a prey species must be considered when ranking prey.
Despite the formality of the conditions required by many applications of foraging theory in modem settings, these models can be applied more loosely to generate qualitative or rank-ordered predictions about the types of small game that prehistoric humans are expected to capture under specific demographic conditions. Though foraging models assume that human hunters tend to maximize cost/benefits, they do not assume that human hunters consciously forage with efficiency in mind. Humans are intelligent social animals who make some foraging decisions based on economic criteria and some on seemingly noneconomic criteria. However, even if noneconomic decisions accounted for a large part of human subsistence activities, they still will not mask the signature of
else, and though social factors have a role to play, recent studies consistently demonstrate that humans meet nutritional needs by taking advantage of the highest quality resources they can effectively and safely procure (e.g., Kelly 1995; O'Connell and Hawkes 1982;
Smith and Winterhalder 1992; Winterhalder 1986).
Predicting Demographic Pressure from Human Prey Choice Variability in the ecological characteristics of prey species allows the derivation of expectations about the effects of human hunting pressure. Each prey species possesses a distinctive suite of characteristics that constrain the energy and hunting techniques humans must invest in their capture. Prey species will also respond demographically in different though clearly predictable ways to human hunting pressure. Two characteristics in particular play a large role in determining the cost/benefits and demographic responses of prey populations. First, the escape strategy of the prey strongly influences the cost of procurement. Second, population turnover and individual growth rates determine the susceptibility of a species to hunting pressure, the rate of the population's recovery, and ultimately its future availability to human hunters.
Escape Strategy ("Catchability") Variation in escape strategy is of considerable importance when ranking animals of similar body size. Unlike their large game counterparts, the small game species commonly hunted by Paleolithic foragers show great variability in predator evasion strategies ranging from rapid flight to freezing and hiding. Though technological solutions can be developed to overcome prey escape strategies, pursuit and handling costs
such as partridges and hares, is higher than for slow-moving species such as tortoises.
The latter can usually be captured by hand, clearly a much lower-cost technique than those usually employed in the capture of fast prey types.
Population Turnover (Regeneration) Rates The reproductive characteristics of prey taxa determine the effects of human predation on their populations, irrespective of their food value in human eyes.
Reproductive data on common small prey species from the Natufian period (tortoise, hare, and partridge) are the basis for predator-prey simulations originally presented by Stiner et al. (1999, 2000). These simulations explore the responses of different animal populations to human hunting (see Chapter 6 and Stiner et al. 1999, 2000 for details).
The simulations demonstrate remarkable differences in the population resilience of highand low-turnover species. High-turnover animals quickly replace their populations through rapid growth. They tend to produce many young, experience heavy juvenile mortality, and live relatively short lives. Rapid growth and development permits explosive population growth and give tremendous resilience to high-turnover populations, even under conditions of heavy hunting. In contrast, low-turnover populations (tortoise) regenerate slowly. Adults produce few to many young, but juvenile mortality is high, and most importantly, individual development is slow. Low recruitment combined with slow growth causes low-turnover populations to be particularly susceptible to depletion by overhunting. Differential population resilience in
small game species means that they will respond differently to human hunting pressure:
Summary of Predator-Prey Interactions Like other animals, humans are expected to maximize benefits relative to costs while foraging (Kelly 1995; Stephens and Krebs 1986; Winterhalder 1986). Furthermore, when human population density and hunting intensity are low, human hunters are expected to select resources that produce the greatest returns for the effort of search, pursuit, and capture; either the least expensive to take (e.g., tortoises), or those that provide the largest quantities of energy per hunting episode (e.g., ungulates). As hunting intensity increases, humans will eventually cross a threshold beyond which the most attractive resources will no longer be available in adequate numbers to meet energy requirements, because some highly ranked prey populations shrink as human harvesting rates increase. At this point humans must add less cost effective (low-ranked) resources to their diet. Such animals include fast-moving birds and hares, which are also notorious for their productivity and their ability to withstand much greater harvesting pressure (Stiner et al. 1999, 2000). These model predictions can be directly tested by examining the proportions of game animals in the archaeological record using skeletal remains.
Recent work by Stiner et al. (1999, 2000) uses changes in human prey choice to trace broad regional trends in human demography from the Middle Paleolithic to the Natufian period in the Wadi Meged in Israel. Particular attention is given to small game
of spatial and temporal variation within the Natufian period (ca. 13,000 -10,500 B.P.).
The methods previously established to investigate broad regional trends are adapted here to address questions of site use intensity within a relatively short cultural period (see also Munro 1999; Surovell 1999). At issue are trends in prehistoric human demography on local and regional scales during a cultural period lasting about 2500 years.
Understanding of these trends is based on faunal indicators of human hunting intensity.
Local analyses monitor change in the intensity of site use, whereas regional analyses seek to gauge human hunting pressure in the Mediterranean Levant.